Distribution of Matrix Metalloproteinases in Human Atherosclerotic Carotid Plaques and Their Production by Smooth Muscle Cells and Macrophage Subsets.

PURPOSE: In this study, the potential of matrix metalloproteinase (MMP) sense for detection of atherosclerotic plaque instability was explored. Secondly, expression of MMPs by macrophage subtypes and smooth muscle cells (SMCs) was investigated. PROCEDURES: Twenty-three consecutive plaques removed during carotid endarterectomy were incubated in MMPSense™ 680 and imaged with IVIS® Spectrum. mRNA levels of MMPs, macrophage markers, and SMCs were determined in plaque specimens, and in in vitro differentiated M1 and M2 macrophages. RESULTS: There was a significant difference between autofluorescence signals and MMPSense signals, both on the intraluminal and extraluminal sides of plaques. MMP-9 and CD68 messenger RNA (mRNA) expression was higher in hot spots, whereas MMP-2 and αSMA expression was higher in cold spots. In vitro M2 macrophages had higher mRNA expression of MMP-1, MMP-9, MMP-12, and TIMP-1 compared to M1 macrophages. CONCLUSION: MMP-9 is most dominantly MMP present in atherosclerotic plaques and is produced by M2 rather than M1 macrophages.

Does reduction of disease activity improve early markers of cardiovascular disease in newly diagnosed rheumatoid arthritis patients?

OBJECTIVE: The incidence of cardiovascular disease (CVD) is increased in RA. This study was designed to evaluate whether a reduction in disease activity influences early markers of CVD. METHODS: In a prospective longitudinal study, 58 newly diagnosed RA patients and 58 age- and sex-matched healthy controls (HCs) were included. Endothelial dysfunction was measured by small artery elasticity (SAE) and endothelial cell activation was assessed by measuring soluble vascular cellular activation molecule 1(sVCAM-1) and von Willebrand factor (vWF). Advanced glycation end products (AGEs) were quantified by skin autofluorescence. After 1 year, measurements were repeated in all RA patients. RESULTS: At entry, SAE was decreased in RA vs HCs [median 3.4 ml/mmHg100 (range 1.2-9.0) vs 6.1 (range 5.0-15.3), P < 0.0001] and sVCAM-1 and vWF were increased: 391 ng/ml (range 256-680) vs 341 (range 223-691) (P = 0.0015) and 120 ng/ml (range 26.5-342) vs 99 (range 22-298) (P = 0.02), respectively. SAE was inversely correlated with the 28-joint DAS (DAS28; r = -0.31, P = 0.016). AGEs were increased by 2.55 arbitrary units (range 1.29-4.65) vs 2.12 (range 1.32-3.82) in HCs (P = 0.003). In multivariate analysis, the presence of RA, age and systolic blood pressure were independently and inversely related to SAE. After 1 year, SAE had significantly improved in RA, from 3.4 (range 1.2-9.0) to 3.8 (range 1.5-10.3) (P = 0.03). CONCLUSION: Endothelial dysfunction is present in newly diagnosed RA patients, independently of traditional risk factors and is inversely correlated with disease activity. By reducing disease activity, endothelial dysfunction improves, although not to normal values. Also, a reduction in disease activity targeting traditional risk factors remains important in preventing CVD in RA.

Folate receptor-ß imaging using 99mTc-folate to explore distribution of polarized macrophage populations in human atherosclerotic plaque.

UNLABELLED: In atherosclerotic plaques, the risk of rupture is increased at sites of macrophage accumulation. Activated macrophages express folate receptor-ß (FR-ß), which can be targeted by folate coupled to radioactive ligands to visualize vulnerability. The aim of this study was to explore the presence of activated macrophages in human atherosclerotic plaques by (99m)Tc-folate imaging and to evaluate whether this technique can discriminate between an M1-like and M2-like macrophage phenotype. METHODS: Carotid endarterectomy specimens of 20 patients were incubated with (99m)Tc-folate, imaged using micro-SPECT, and divided into 3-mm slices. The mean accumulation was calculated per slice, and the distribution of M1-like and M2-like macrophages per slice was quantified by immunohistochemical staining for CD86 as well as inducible nitric oxide synthase (iNOS) for M1 and CD163 and FR-ß for M2 macrophages. Monocytes from healthy donors were differentiated toward M1-like or M2-like phenotype by in vitro culturing. Messenger RNA levels of specific M1 and M2 markers were measured by reverse-transcription polymerase chain reaction and expression of FR-ß, CD86, and CD163 by flow cytometry. RESULTS: There was a heterogeneous accumulation of (99m)Tc-folate in plaques (median, 2.45 [0.77-6.40] MBq/g). Slices with the highest (99m)Tc-folate accumulation of each plaque showed significantly more expression of FR-ß and CD163, compared with slices with the lowest (99m)Tc-folate accumulation, which showed significantly more expression of iNOS. In in vitro polarized macrophages, messenger RNA expression of FR-ß, mannose receptor, IL-10, and matrix metalloproteinase-9 was significantly increased in M2-like macrophages, compared with M1-like macrophages. On a receptor level, CD86 was shown to be overexpressed on M1-like macrophages whereas FR-ß and CD163 were overexpressed on M2-like macrophages measured by flow cytometry. CONCLUSION: Higher numbers of M2-like macrophages were present in areas of high (99m)Tc-folate accumulation than areas with low accumulation. It is anticipated that (99m)Tc-folate imaging using SPECT as a marker for M2-like macrophages in atherosclerosis might be a good indicator for plaque vulnerability.

Targeted folate receptor ß fluorescence imaging as a measure of inflammation to estimate vulnerability within human atherosclerotic carotid plaque.

UNLABELLED: The probability of atherosclerotic plaque rupture and its thrombotic sequelae are thought to be increased at sites of macrophage accumulation. Folate receptor ß (FR-ß) is present on activated macrophages but not on quiescent macrophages or other immune cells. By conjugating the ligand folate with a fluorescent contrast agent, fluorescein isothiocyanate (FITC), we aimed to explore the potential role of FR-ß fluorescence imaging in the distinction of vulnerable sites from more stable regions. METHODS: Carotid specimens were taken from 20 patients and incubated with folate-FITC for 30 min. Ex vivo fluorescence imaging was performed to determine the exact location of folate-FITC uptake. Sections displaying regions of high uptake (determined as hot spots) were compared with sections showing low uptake (cold spots) through immunohistochemistry and real-time quantitative reverse-transcription polymerase chain reaction for FR-ß. RESULTS: Hot spots showed significantly higher folate-FITC uptake than cold spots (P < 0.001). Hot spots tended to contain more macrophages and areas of hypoxia than cold spots. A positive correlation between messenger RNA levels of CD68 (marker for macrophages), FR-ß (r = 0.53, P = 0.045), and hypoxia-inducible factor-1α expression (marker for intraplaque hypoxia; r = 0.55, P = 0.034) was found. CONCLUSION: Compared with areas with low folate-FITC uptake, areas of high folate-FITC uptake within human atherosclerotic plaques had an increased number of activated macrophages and higher areas of hypoxia. These characteristics of vulnerability imply that molecular imaging of FR-ß through folate conjugates might be a good indicator for plaque vulnerability in future noninvasive imaging studies.

Macrophage folate receptor-ß (FR-ß) expression in auto-immune inflammatory rheumatic diseases: a forthcoming marker for cardiovascular risk?

In patients with systemic auto-immune inflammatory rheumatic diseases (AIIRD) like rheumatoid arthritis the prevalence of cardiovascular disease (CVD) is increased. In the pathogenesis of AIIRD and atherosclerosis many similarities can be found in the process underlying CVD. Accumulation of inflammatory cells, in particular macrophages at the site of inflammation producing inflammatory mediators serve as a prominent feature in both systemic inflammation and atherosclerosis. Two different subtypes of macrophages have been described in recent literature namely classically activated macrophages (M1) and alternatively activated macrophages (M2). Alternatively activated macrophages are characterized by low CD14 and high CD163 expression. Macrophages expressing CD14 (M1) have been identified within atherosclerotic plaques, whereas CD14 low macrophages are abundant in vessels without atherosclerosis. Depending on the environment and responses to different stimuli, macrophages in plaques can express diverse pro and anti-atherogenic functions. The balance of these different activation profiles influences atheroma evolution and outcome. Nowadays, influx of macrophages is recognized as a very important feature of the pathogenesis of plaque formation. Activated macrophages accumulate at the sites of inflammation and can therefore be exploited to better visualize inflammatory responses in atherosclerosis. Furthermore, activated (but not resting) macrophages possess a functionally active receptor for folate (FR-ß), but it is not completely clear which subtype of this activated macrophages expresses this receptor and whether the expression of FR-ß is restricted to only one of the macrophage subsets. Although future research needs to be done to investigate FR-ß expression and function within inflamed tissues, the expression of functional FR-ß on tissue macrophages likely occurs during activation. Therefore, expression of FR-ß on activated macrophages holds a promising potential for early diagnosis and better analysis of optimal treatment regiments of vascular diseases in association with systemic diseases.